There are known internal combustion engines using the spark ignition to initiate combustion of fuel/air mixture within each combustion chamber. There are known or proposed internal combustion engines enabling compression auto-ignition after compressing fuel/air mixture charge within each combustion chamber (see Patent Documents 1 to 3). In the internal combustion engines of the compression auto-ignition type, various kinds of ideas are made, including changes or modifications of the shape of each combustion chamber (see Patent Document 4) and changes or modifications of the intake and exhaust systems (see Patent Document 5).
The compression auto-ignition internal combustion engines may employ combustion after diluting the fresh charge with exhaust gas recirculation (EGR) by overlapping the intake and exhaust timings. In this case, there is a reduction in CO2 emission as compared to the spark-ignition combustion.
The combustion temperature initiated by the compression auto-ignition is low. Thus, the compression auto-ignition combustion provides little nitrogen oxide (NOx) emission. Therefore, the compression auto-ignition combustion is expected to make good contributions to a reduction in nitrogen oxide emission which reduction has been aimed at for combustion of diluted lean charge.